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AIR-2: An Aurora/Ipl1-related protein kinase associated with chromosomes and midbody microtubules is required for polar body extrusion and cytokinesis in Caenorhabditis elegans embryos.

Schumacher JM, Golden A, Donovan PJ - J. Cell Biol. (1998)

Bottom Line: Unlike other Aurora/Ipl1-related kinases, the Caenorhabditis elegans orthologue, AIR-2, is associated with meiotic and mitotic chromosomes.AIR-2 also remains associated with both extruded polar bodies.In the embryo, AIR-2 is found on metaphase chromosomes, moves to midbody microtubules at anaphase, and then persists at the cytokinesis remnant.

View Article: PubMed Central - PubMed

Affiliation: Cell Biology of Development and Differentiation Group, ABL-Basic Research Program, NCI-Frederick Cancer Research and Development Center, Frederick, Maryland 21702, USA.

ABSTRACT
An emerging family of kinases related to the Drosophila Aurora and budding yeast Ipl1 proteins has been implicated in chromosome segregation and mitotic spindle formation in a number of organisms. Unlike other Aurora/Ipl1-related kinases, the Caenorhabditis elegans orthologue, AIR-2, is associated with meiotic and mitotic chromosomes. AIR-2 is initially localized to the chromosomes of the most mature prophase I-arrested oocyte residing next to the spermatheca. This localization is dependent on the presence of sperm in the spermatheca. After fertilization, AIR-2 remains associated with chromosomes during each meiotic division. However, during both meiotic anaphases, AIR-2 is present between the separating chromosomes. AIR-2 also remains associated with both extruded polar bodies. In the embryo, AIR-2 is found on metaphase chromosomes, moves to midbody microtubules at anaphase, and then persists at the cytokinesis remnant. Disruption of AIR-2 expression by RNA- mediated interference produces entire broods of one-cell embryos that have executed multiple cell cycles in the complete absence of cytokinesis. The embryos accumulate large amounts of DNA and microtubule asters. Polar bodies are not extruded, but remain in the embryo where they continue to replicate. The cytokinesis defect appears to be late in the cell cycle because transient cleavage furrows initiate at the proper location, but regress before the division is complete. Additionally, staining with a marker of midbody microtubules revealed that at least some of the components of the midbody are not well localized in the absence of AIR-2 activity. Our results suggest that during each meiotic and mitotic division, AIR-2 may coordinate the congression of metaphase chromosomes with the subsequent events of polar body extrusion and cytokinesis.

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air-2(RNAi) embryos execute multiple cell  cycles in the absence of cytokinesis. (A–C) Embryos  were dissected from hermaphrodites that had been injected with double-stranded  RNA corresponding to the  entire air-2 cDNA. air-2  (RNAi) embryos were fixed  and stained with DAPI (A),  AIR-2 (B), and α-tubulin antibodies (C). (A) air-2(RNAi) embryos accumulate DNA, (B) do not express a detectable level of AIR-2, and (C) contain multiple microtubule asters. The embryos appear to execute multiple cell cycles without completing cytokinesis. As revealed by tubulin staining  (C), some of the embryos appear to be in interphase whereas others are in mitosis. Bar, 20 μm.
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Figure 7: air-2(RNAi) embryos execute multiple cell cycles in the absence of cytokinesis. (A–C) Embryos were dissected from hermaphrodites that had been injected with double-stranded RNA corresponding to the entire air-2 cDNA. air-2 (RNAi) embryos were fixed and stained with DAPI (A), AIR-2 (B), and α-tubulin antibodies (C). (A) air-2(RNAi) embryos accumulate DNA, (B) do not express a detectable level of AIR-2, and (C) contain multiple microtubule asters. The embryos appear to execute multiple cell cycles without completing cytokinesis. As revealed by tubulin staining (C), some of the embryos appear to be in interphase whereas others are in mitosis. Bar, 20 μm.

Mentions: To further characterize air-2(RNAi) lethality, embryos dissected from injected mothers were fixed and stained with DAPI as well as antibodies specific for AIR-2 and α-tubulin. Immunofluorescent analysis revealed that each embryo consisted of an extremely polyploid single cell (Fig. 7 A). AIR-2 staining was absent (Fig. 7 B), and α-tubulin staining revealed either an interphase-like array of microtubules or numerous microtubule asters in each cell (Fig. 7 C). These results suggest that each air-2(RNAi) embryo has undergone multiple cycles of DNA replication and centrosome duplication without completing a single round of cytokinesis.


AIR-2: An Aurora/Ipl1-related protein kinase associated with chromosomes and midbody microtubules is required for polar body extrusion and cytokinesis in Caenorhabditis elegans embryos.

Schumacher JM, Golden A, Donovan PJ - J. Cell Biol. (1998)

air-2(RNAi) embryos execute multiple cell  cycles in the absence of cytokinesis. (A–C) Embryos  were dissected from hermaphrodites that had been injected with double-stranded  RNA corresponding to the  entire air-2 cDNA. air-2  (RNAi) embryos were fixed  and stained with DAPI (A),  AIR-2 (B), and α-tubulin antibodies (C). (A) air-2(RNAi) embryos accumulate DNA, (B) do not express a detectable level of AIR-2, and (C) contain multiple microtubule asters. The embryos appear to execute multiple cell cycles without completing cytokinesis. As revealed by tubulin staining  (C), some of the embryos appear to be in interphase whereas others are in mitosis. Bar, 20 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2132979&req=5

Figure 7: air-2(RNAi) embryos execute multiple cell cycles in the absence of cytokinesis. (A–C) Embryos were dissected from hermaphrodites that had been injected with double-stranded RNA corresponding to the entire air-2 cDNA. air-2 (RNAi) embryos were fixed and stained with DAPI (A), AIR-2 (B), and α-tubulin antibodies (C). (A) air-2(RNAi) embryos accumulate DNA, (B) do not express a detectable level of AIR-2, and (C) contain multiple microtubule asters. The embryos appear to execute multiple cell cycles without completing cytokinesis. As revealed by tubulin staining (C), some of the embryos appear to be in interphase whereas others are in mitosis. Bar, 20 μm.
Mentions: To further characterize air-2(RNAi) lethality, embryos dissected from injected mothers were fixed and stained with DAPI as well as antibodies specific for AIR-2 and α-tubulin. Immunofluorescent analysis revealed that each embryo consisted of an extremely polyploid single cell (Fig. 7 A). AIR-2 staining was absent (Fig. 7 B), and α-tubulin staining revealed either an interphase-like array of microtubules or numerous microtubule asters in each cell (Fig. 7 C). These results suggest that each air-2(RNAi) embryo has undergone multiple cycles of DNA replication and centrosome duplication without completing a single round of cytokinesis.

Bottom Line: Unlike other Aurora/Ipl1-related kinases, the Caenorhabditis elegans orthologue, AIR-2, is associated with meiotic and mitotic chromosomes.AIR-2 also remains associated with both extruded polar bodies.In the embryo, AIR-2 is found on metaphase chromosomes, moves to midbody microtubules at anaphase, and then persists at the cytokinesis remnant.

View Article: PubMed Central - PubMed

Affiliation: Cell Biology of Development and Differentiation Group, ABL-Basic Research Program, NCI-Frederick Cancer Research and Development Center, Frederick, Maryland 21702, USA.

ABSTRACT
An emerging family of kinases related to the Drosophila Aurora and budding yeast Ipl1 proteins has been implicated in chromosome segregation and mitotic spindle formation in a number of organisms. Unlike other Aurora/Ipl1-related kinases, the Caenorhabditis elegans orthologue, AIR-2, is associated with meiotic and mitotic chromosomes. AIR-2 is initially localized to the chromosomes of the most mature prophase I-arrested oocyte residing next to the spermatheca. This localization is dependent on the presence of sperm in the spermatheca. After fertilization, AIR-2 remains associated with chromosomes during each meiotic division. However, during both meiotic anaphases, AIR-2 is present between the separating chromosomes. AIR-2 also remains associated with both extruded polar bodies. In the embryo, AIR-2 is found on metaphase chromosomes, moves to midbody microtubules at anaphase, and then persists at the cytokinesis remnant. Disruption of AIR-2 expression by RNA- mediated interference produces entire broods of one-cell embryos that have executed multiple cell cycles in the complete absence of cytokinesis. The embryos accumulate large amounts of DNA and microtubule asters. Polar bodies are not extruded, but remain in the embryo where they continue to replicate. The cytokinesis defect appears to be late in the cell cycle because transient cleavage furrows initiate at the proper location, but regress before the division is complete. Additionally, staining with a marker of midbody microtubules revealed that at least some of the components of the midbody are not well localized in the absence of AIR-2 activity. Our results suggest that during each meiotic and mitotic division, AIR-2 may coordinate the congression of metaphase chromosomes with the subsequent events of polar body extrusion and cytokinesis.

Show MeSH
Related in: MedlinePlus